While contemplating the objects of the senses, a person develops attachment for them, and from such attachment lust develops, and from lust anger arises.
From anger, complete delusion arises, and from delusion bewilderment of memory. When memory is bewildered, intelligence is lost, and when intelligence is lost one falls down again into the material pool.
It is evident from the above verses that attachment causes an individual to fall back into the material pool. It is not an instant one but it is a series of steps which are in fact quite subtle and they may occur without our awareness.
When the senses find something that gives it pleasure, it attaches to it. This can be for any of the five senses- eyes,ears,nose,tongue and skin. For example, an ice cream which is a favorite for millions, pleasures the tongue and eyes; music pleasures the ears and so on. Once the senses attach to the objects of their desire, the senses develop a lust to obtain/attain that object.
What is Lust?
The Supreme Personality of Godhead said: It is lust only, Arjuna which is born of contact with the the material mode of passion and later transformed into wrath, and which is the all-devouring sinful enemy of this world.
When a living entity comes in contact with the material creation, his love for Krishna gets tarnished with lust i.e., due to attachment, this love which we have for the Supreme Father gets transformed to lust. Love for Krishna can be transformed to lust by modes of material nature but transforming lust to love is extremely exasperating. When lust unsatisfied, it turns into wrath which is transformed into illusion. Therefore, lust is the greatest enemy which induces the pure living entity to remain entangled in this material world. It drags us from the plane of reality and truth and drowns us in the ocean of nescience.
Where does this lust originate from? The answer is also given by Krishna:
The senses, the mind and the intelligence are the sitting places of this lust. Through them lust covers the real knowledge of the living entity and bewilders him.
Mind is the center of all activities of the senses. Thus when we hear about the sense objects the mind generally becomes the reservoir of all ideas of sense gratification and as a result, the mind and the senses become the storehouse of lust. Intelligence is the immediate neighbor the spirit soul. Lusty intelligence influences the spirit soul to attain false ego and identify itself with matter. The spirit soul thus becomes addicted to enjoying the material senses and mistakes this as true happiness.
Therefore, O Arjuna, best of Bharatas, in the very beginning curb this great symbol of sin [lust] by regulating the senses, and slay this destroyer of knowledge and self realization.
Thus the Supreme Lord asks us to slay this enemy in the very beginning of the spiritual journey as it hinders the entity from attaining self realization. Lust is only the perverted reflection of love of God which is natural of every living being. If one is educated during the genesis, that natural love for God cannot deteriorate. Turning lust into love is the highest perfection.